Resource allocation in a radio communication system

ABSTRACT

A method of using resource blocks in a communication system with a plurality of Base Stations (BSs), including assigning resource blocks to a first BS, the first BS communicating to a second BS a message comprising information about at least one resource block assigned to the first BS and not planned to be used by the first BS, and the second BS receiving the message. Optionally, the second BS using the at least one resource block. Related apparatus and methods are also described.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/607,901 filed on Sep. 10, 2012, which is a continuation of U.S.patent application Ser. No. 12/495,896 filed on Jul. 1, 2009, thecontents of which are incorporated herein by reference in theirentirety.

FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to acommunication system and, more particularly, but not exclusively, to acellular communication system, and even more particularly, but notexclusively, to resource allocation in a cellular communication system.

A non-limiting example of resource allocation is time-divisionmultiplexing, which separates time slots for forward and return signals.Non-limiting examples of Time Division Duplexing systems are: W-CDMA(for indoor use); UMTS-TDD's TD-CDMA air interface; the TD-SCDMA system;DECT; IEEE 802.16 WiMAX TDD; half-duplex packet mode networks based oncarrier sense multiple access, for example 2-wire or hubbed Ethernet;Wireless local area networks; and Bluetooth, can all be considered asTime Division Duplex systems.

For example, in systems using Orthogonal Frequency Division MultipleAccess (OFDMA), such as Time Division Duplexing (TDD) and FrequencyDivision Duplexing (FDD) systems, a two dimensional frame is defined inorder to assign frequencies (e.g. subcarriers) and determine timedivision. The two dimensional frame has time as one dimension andfrequency as another dimension. Within each frame frequencies and a timeslot are assigned for use, for example for a Base Station (BS) totransmit at a downlink (DL) time slot, to a Mobile Station (MS), and toreceive at an uplink (UL) time slot, from a MS.

Background art includes a publication named “Mobile WiMAX—Part I: ATechnical Overview and Performance Evaluation”, published August 2006 bythe WiMAX Forum, and available on the World Wide Web at:wwwdotwimaxforumdotorg/news/downloads/Mobile_WiMAX_Part1_Overview_and_Performance.pdf.

SUMMARY OF THE INVENTION

The present invention, in some embodiments thereof, allocates resourceuse in a cellular communication system by having base stationscommunicate availability of free resources.

According to an aspect of some embodiments of the present inventionthere is provided a method of using resource blocks in a communicationsystem with a plurality of Base Stations (BSs), including assigningresource blocks to a first BS, the first BS communicating to a second BSa message including information about at least one resource blockassigned to the first BS and not planned to be used by the first BS, andthe second BS receiving the message.

According to some embodiments of the invention, further including thesecond BS using the at least one resource block.

According to some embodiments of the invention, the communication systemincludes a Time Division Duplex (TDD) communication system. According tosome embodiments of the invention, the communication system includes aFrequency Division Duplex (FDD) communication system.

According to some embodiments of the invention, further including asecond BS communicating a message including information about at leastone resource block assigned to the second BS and not planned to be usedby the second BS, and at least one other BS than the second BS receivingthe message. According to some embodiments of the invention, furtherincluding the at least one other BS than the second BS using the atleast one resource block assigned to the second BS.

According to some embodiments of the invention, communicating messagesoccurs between the BSs in a peer-to-peer fashion. According to someembodiments of the invention, communicating messages occurs between theBSs in a master-slave fashion, and further including a master BSinstructing a slave BS which data to transmit in the at least one of theresource blocks.

According to some embodiments of the invention, the resource blocks aredivided into a plurality of groups, and the resource blocks are used inan order based, at least in part, according to the groups. According tosome embodiments of the invention, at least two different BSs each haveat least two different groups for the resource blocks.

According to some embodiments of the invention, the communication systemis a WiMAX system. According to some embodiments of the invention, thecommunication system is an LTE system.

According to an aspect of some embodiments of the present inventionthere is provided a method of using resource blocks in a communicationsystem with a plurality of Base Stations (BSs), including assigningresource blocks to a first BS and to a second BS, having at least thefirst BS transmit first data about its planned use of resource blocks,having at least the second BS receive the transmitted first data, havingat least the second BS transmit second data to the first BS, and havingthe first BS transmit the second data to a Mobile Station (MS) using atleast one of the resource blocks assigned to the first BS.

According to an aspect of some embodiments of the present inventionthere is provided a method of using resource blocks in a communicationsystem with a plurality of Base Stations (BSs), including at least twoneighboring BSs scheduling use of resource blocks, to be used in aspecific time period, each one of the at least two neighboring BSs atfirst planning to use resource blocks defined as primary resources foreach one of the at least two neighboring BSs, the at least two BSscommunicating a first message including information about at least oneresource block each one of the at least two BSs is not planning to use,to their adjacent neighbors, the at least two BSs receiving the message,the at least two BSs scheduling use of the resource blocks referenced inthe first message, and the at least two BSs executing their schedule.

According to some embodiments of the invention, further including, afterthe at least two BSs scheduling use of the resource blocks referenced inthe first message the at least two BSs communicating a second messageincluding information about at least one additional resource block eachone of the at least two BSs is not planning to use, the at least two BSsreceiving the second message, and the at least two BSs scheduling use ofthe additional resource blocks, before the at least two BSs executetheir schedule.

According to an aspect of some embodiments of the present inventionthere is provided a method of using resource blocks in a communicationsystem with a plurality of Base Stations (BSs), including at least threeneighboring BSs, of which at least two BSs are not adjacent neighbors ofeach other, scheduling use of resource blocks, to be used in ancommunication frame, each one of the three neighboring BSs at firstscheduling use of resource blocks defined as primary resources for eachone of the three neighboring BSs, the at least three BSs sending a firstmessage including information about resource blocks not scheduled foruse to other BSs of the at least three BSs, the at least three BSsreceiving the first message, the at least three BSs scheduling use ofthe resource blocks referenced in the first message, and the at leastthree BSs executing their schedule.

According to some embodiments of the invention, further including, afterthe at least three BSs scheduling use of the resource blocks referencedin the first message the at least three BSs sending a second messageincluding information about at least one additional resource block eachone of the at least three BSs is not planning to use, the at least threeBSs receiving the second message, and the at least three BSs schedulinguse of the additional resource blocks, before the at least three BSsexecute their schedule.

According to some embodiments of the invention, further includingadditional cycles of at least one of the at least three BSs sending amessage including information about at least one more additionalresource block the at least one BS is not planning to use to the othersof the at least three BSs, the others of the at least three BSsreceiving the message, and at least one of the at least three BSsscheduling use of the at least one more additional resource block,before the at least three BSs execute their schedule.

Unless otherwise defined, all technical and/or scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which the invention pertains. Although methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of embodiments of the invention, exemplarymethods and/or materials are described below. In case of conflict, thepatent specification, including definitions, will control. In addition,the materials, methods, and examples are illustrative only and are notintended to be necessarily limiting.

Implementation of the method and/or system of embodiments of theinvention can involve performing or completing selected tasks manually,automatically, or a combination thereof. Moreover, according to actualinstrumentation and equipment of embodiments of the method and/or systemof the invention, several selected tasks could be implemented byhardware, by software or by firmware or by a combination thereof usingan operating system.

For example, hardware for performing selected tasks according toembodiments of the invention could be implemented as a chip or acircuit. As software, selected tasks according to embodiments of theinvention could be implemented as a plurality of software instructionsbeing executed by a computer using any suitable operating system. In anexemplary embodiment of the invention, one or more tasks according toexemplary embodiments of method and/or system as described herein areperformed by a data processor, such as a computing platform forexecuting a plurality of instructions. Optionally, the data processorincludes a volatile memory for storing instructions and/or data and/or anon-volatile storage, for example, a magnetic hard-disk and/or removablemedia, for storing instructions and/or data. Optionally, a networkconnection is provided as well. A display and/or a user input devicesuch as a keyboard or mouse are optionally provided as well.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are herein described, by way ofexample only, with reference to the accompanying drawings. With specificreference now to the drawings in detail, it is stressed that theparticulars shown are by way of example and for purposes of illustrativediscussion of embodiments of the invention. In this regard, thedescription taken with the drawings makes apparent to those skilled inthe art how embodiments of the invention may be practiced.

In the drawings:

FIG. 1 is a simplified illustration of a prior art Orthogonal FrequencyDivision Multiple Access (OFDMA) frame;

FIG. 2 is a simplified illustration of cells in a prior art cellularcommunication system;

FIG. 3 is a simplified illustration of the operation of a reuse ⅓ frame;

FIG. 4 is a simplified illustration of two exemplary Base Stations(BSs), communicating with several exemplary Mobile Stations (MSs);

FIG. 5A is a simplified illustration of two BSs constructed andoperating according to an embodiment of the present invention;

FIG. 5B is a simplified illustration of two BSs constructed andoperating according to an alternative example embodiment of the presentinvention, communicating with several MSs;

FIG. 6 is a simplified illustration of the BSs and MSs of FIG. 5B, in analternative application of the example embodiment of FIG. 5B;

FIG. 7 is a simplified illustration of a grouping of resource blocks ina frame constructed and operating according to an example embodiment ofthe present invention;

FIG. 8 is a simplified illustration of a network of base stationsconstructed and operating according to an example embodiment of thepresent invention, showing groups of reuse sub-channels;

FIG. 9 is a simplified flow chart illustration of a method for planningresource assignment, operating according to an example embodiment of thepresent invention;

FIG. 10 is a simplified illustration of communications and decisions ona timeline, with reference to base stations constructed and operationalaccording to the example embodiment of FIG. 9; and

FIG. 11 is a simplified flow chart illustration of a method for planningresource assignment, operating according to an alternative exampleembodiment of the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to acommunication system and, more particularly, but not exclusively, to acellular communication system, and even more particularly, but notexclusively, to resource allocation in a cellular communication system.

The present invention, in some embodiments thereof, improves resourceuse in a cellular communication system by having base stations (BSs)communicate availability of free resources. The BSs use the availablefree resources for improving communications with mobile stations (MSs).By improving resource use, the present invention, in some embodimentsthereof, enables, by way of a non-limiting example, communicatingbetween a BS and a MS at a higher data rate. The higher data rateenables improving communication, whether by sending more data in a giventime, and/or sending redundant data which particularly enablesoptionally sending more error correction overhead data.

A “resource block” is hereby defined as a resource which, when used bymore than one communication station, may cause interference.

An example of a resource block in the field of OFDMA communications isoptionally a time slot in one sub-channel.

The term “allocate” in all its grammatical forms is used throughout thepresent specification and claims interchangeably with the term “assign”and its corresponding grammatical forms.

Allocating and/or assigning resource blocks are typically done as partof a Radio Resource Management (RRM) plan. By way of a non-limitingexample, the RRM in a communication network is typically produced by aRadio Network Controller (RNC).

In a prior art cellular network many resource blocks go unused, bydesign. For example, in reuse ⅓ schemes, many resource blocks may beunused by a BS but cannot be reallocated to other BSs operating at thesame frequency channel.

In an exemplary embodiment of the invention, some or all of the unusedresource blocks are reallocated to other BSs. The unused resource blocksare used, by way of non-limiting examples, to improve totalcommunication volume, and/or for a diversity scheme to improve thereliability of a message signal by utilizing two or more communicationchannels with different characteristics. Optionally the diversity schemeimproves the signal to noise ratio (SNR) of the message. Optionally thediversity scheme enables receiving the message at a greater distancefrom a BS. Optionally the unused resource blocks are used for sendingsome packets of a packet communication twice, thereby increasing alikelihood of correct reception without errors.

Reallocating the unused resource blocks is performed rapidly, optionallyin less than one time slot, thereby enabling reallocation of the unusedresource blocks close enough to real-time to use all or most of theunused resource blocks by the next time slot after their being availableis discovered. An example embodiment of the allocation method isdescribed below with reference to FIGS. 8-11.

In some cases, the additional resource blocks may be prone to a lowerSNR, due to interference.

In some embodiments of the invention, the same data may be transmittedfrom two or more BSs to the same MS, thereby improving chances of databeing uncorrupted even if the data is sent via the additional resourceblocks.

The lower SNR may not be suitable for some uses, but may be suitable forother uses, such as, by way of a non-limiting example, data networkswith error correction or with repeat transmission such as Ethernet.

In some embodiments of the present invention, there exists amaster-slave relationship between base stations, so that a master BSdetermines which BS uses the free resource blocks.

In some example embodiments of the invention, the master-slaverelationship between base stations is optionally set upon BSinstallation, optionally according to known characteristics of the BS,such as expected MS density and/or expected message traffic for the BS.

In some example embodiments of the invention, the master-slaverelationship between base stations is optionally set and/or changeddynamically, optionally according to a history of relative MS densityand/or relative message traffic for the BSs.

In some example embodiments of the invention, the master-slaverelationship between base stations is optionally decided by a centralarbitrator, optionally according to dynamic characteristics of the BS,such as expected MS density and/or expected message traffic for the BS.

In some example embodiments of the invention, the master-slaverelationship between base stations is optionally set and/or changeddynamically and as a real-time change to changing conditions.

In some embodiments of the invention, the master-slave relationship isoptionally defined between base stations by a mobile station incommunication with base stations which are candidates for themaster-slave relationship.

In some embodiments of the invention, the master-slave relationship isdefined between base stations with reference to a specific data channeland/or one or more specific sub-channels.

In some embodiments of the invention, the master-slave relationship isdefined between base stations such that a first base station is masterover a second base station with reference to specific data and/or aspecific sub-channel and/or a group of resource blocks, and the secondbase station is master over the first base station with reference toanother specific data and/or another specific sub-channel and/or anothergroup of resource blocks.

In some embodiments of the invention, the master-slave relationship isdefined between base stations with reference to a chunk of data, and/oran ad-hoc, temporary data channel, such as, by way of a non-limitingexample, to transmit a movie; to transmit, broadcast, and/or multicastother chunks of data; and for point-to-point transmission of a chunk ofdata.

For purposes of better understanding some embodiments of the presentinvention, as illustrated in FIGS. 5-11 of the drawings, reference isnow made to FIG. 1, which is a simplified illustration of a prior artOFDMA frame 100.

The frame 100 has a horizontal time axis 101, and a vertical frequencyaxis 102. The frequency axis 102 depicts several sub-channels 103 104105. The time axis 101 depicts one time slot, subdivided into a MAP zone106, a DL zone 107, and a UL zone 108. The sub-channels are at differentfrequencies. Each frame has a MAP zone, during which a BS transmitsmetadata; a DL zone, during which DL optionally occurs; and a UL zone,during which UL optionally occurs. The metadata optionally includes dataabout resource allocation, such as sub-channel allocation, frequencyallocation, DL time slot allocation, UL time slot allocation.

Reference is now made to FIG. 2, which is a simplified illustration ofcells in a prior art cellular communication system. FIG. 2 depicts, byway of a non-limiting example, 3 cells 201 202 203. Signal strength isgood at and near cell centers 211 212 213. Signals at cell edges 221 222223 are weaker, and also typically suffer interference from signals inneighboring cells, because at cell edges MSs typically pick up signalsfrom BSs of more than one cell.

Frequency allocation is sometimes maintained at frequency reuse one.Frequency reuse one is a reuse scheme which is achieved when all sectorswithin a cell and all cells within a network operate on a same frequencychannel. However, frequency reuse one (reuse 1) in a cellular networkmay cause users at a cell edge to get degraded signals due tointerference from adjacent cells using the same frequencies.

Mobile WiMAX (Worldwide Interoperability for Microwave Access), by wayof example, addresses the issue of interference from adjacent cells byusing a Partially Used Sub-Carrier (PUSC) scheme. MSs at a cell edge areonly allowed to operate on a fraction of all available sub-channels. Thesub-channel fraction is allocated in such a way that adjacent cells'edges operate on different sets of sub-channels. This is calledfractional frequency use.

Taken from a base station's point of view, some sub-channels of a basestation are at some times left unused, since they serve a neighboringbase station under a PUSC scheme.

In PUSC reuse 3 (also known as reuse ⅓), only one third of thesub-carriers are used. Assuming neighboring BSs also employ PUSC reuse⅓, but use other thirds of the sub-carriers allocated for reuse ⅓,inter-cell interference can be reduced significantly.

The term “PUSC” in all its grammatical forms is used throughout thepresent specification and claims interchangeably with the term “reuse”and its corresponding grammatical forms and with the term “PUSC reuse”and its corresponding grammatical forms. The term “PUSC” as used hereinrefers to its use with reference to the mobile WiMAX example, asmentioned above.

The term “sub-channel” in all its grammatical forms is used throughoutthe present specification and claims interchangeably with the term“frequency” and its corresponding grammatical forms.

Reference is now made to FIG. 3, which is a simplified illustration ofthe operation of a reuse ⅓ frame 300.

The reuse ⅓ frame 300 includes the horizontal time axis 101 and thevertical frequency axis 102 of FIG. 1. The frequency axis 102 depictsthe several sub-channels 103 104 105 of FIG. 1. The time axis 101depicts the time frame, subdivided into a MAP zone 106, a DL zone 107,and a UL zone 108 as in FIG. 1.

The sub-channels 103 104 105 are divided among BSs, for use incommunication with MSs. By way of a non-limiting example, the reuse ⅓frame 300 allocates a first sub-channel 103 to a first base station BS1(not shown), for use in communication with a first mobile station MS1(not shown). The reuse ⅓ frame 300 also allocates a second sub-channel104 to a second base station BS2 (not shown), for use in communicationwith a second mobile station MS2 (not shown), and a third sub-channel105 to a third base station BS2 (not shown), for use in communicationwith a third mobile station MS2 (not shown). In this fashion thecommunication between three exemplary BSs and three corresponding MSscan occur at the same time on different sub-channels, without producinginterference, according to the reuse ⅓ scheme.

It is noted that other schemes may be used, such as ½, ¼, and so on. Thereuse schemes typically depend on base station physical layout andcommunication conditions, which together influence what portion ofsub-channels need to be allocated for overcoming interference.

It is noted that other sub-channels (not shown) may concurrently be usedby other MSs. More than one sub-channel is typically used by a BSconcurrently. More than one MS typically communicates concurrently witheach BS. FIG. 3 depicts a much-simplified example relative to a typicalreuse ⅓ frame 300.

It is noted that other communication schemes may be used, in which thevertical axis may be divided into sub-channels according to othermethods, appropriate to other communication methods. By way of anon-limiting example, the vertical axis may be divided into sub-channelsaccording to CDMA code space.

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not necessarily limited in itsapplication to the details of construction and the arrangement of thecomponents and/or methods set forth in the following description and/orillustrated in the drawings. The invention is capable of otherembodiments or of being practiced or carried out in various ways.

Reference is now made to FIG. 4, which is a simplified illustration oftwo exemplary base stations (BSs), a first BS, BS1 403, and a second BS,BS2 404, communicating with several exemplary mobile stations (MSs):MS1-1 411, MS1-2 412, MS1-3 413, MS2-1 421, MS2-2 422, MS2-3 423, andMS2-4 424.

Communication data 401 402 reaches the BS1 403 and the BS2 404 via somecommunication medium (not shown). The BS1 403 and the BS2 404communicate with the MS1-1 411, the MS1-2 412, the MS1-3 413, the MS2-1421, the MS2-2 422, the MS2-3 423, and the MS2-4 424 using radio channelcommunication. Separate and distinct, whole resource blocks areallocated to each line of communication: a line of communication 431from the BS1 403 to the MS1-1 411, a line of communication 432 from theBS1 403 to the MS1-2 412, and so on up to a line of communication 437from the BS2 404 to the MS2-4 424.

It is noted that resource blocks allocated to the BSs may be free atcertain times, for a variety of reasons.

By way of a non-limiting example, a resource block may be allocated to aBS according to a partial reuse scheme, and the BS may not be currentlyusing the resource block.

By way of another non-limiting example, a MS may have stoppedcommunicating, leaving the resource blocks allocated for itscommunication free until a new MS requires the resource blocks.

It is noted that it is possible that some MSs consume and produce moretraffic than others. Some BSs communicate with more MSs than other BSs,at any one time. Therefore it is likely that one BS may be loaded muchmore than another BS.

It is noted that when using micro cells and pico cells the variance inloading between BSs is typically larger than with BSs in larger cells.

It is noted that just as there may be unused resource blocks in TDDcommunication systems, there may be unused resource blocks in FrequencyDivision Duplex (FDD) communication systems.

In FDD typically a pair of frequencies is used: one frequency is usedfor uplink and another frequency is used for downlink. The pair offrequencies, per a time slot, may optionally be considered a singleresource block, or the pair of frequencies, per a time slot, mayoptionally be considered two resource blocks.

It is noted that embodiments of the invention apply to FDD as well as tothe TDD examples brought herein.

It is noted that embodiments of the invention apply to various OFDMschemes. One such scheme, by way of a non-limiting example, is named“Long Term Evolution” (LTE), and another such scheme is WiMAX.

Having identified instances of unused resource blocks, some applicationsof reuse of the unused resource blocks will be described.

Reference is now made to FIG. 5A, which is a simplified illustration oftwo BSs 603 604 constructed and operating according to an embodiment ofthe present invention.

The two base stations (BSs) 603 604 are depicted communicating withseveral exemplary mobile stations MS1-1 411, MS1-2 412, MS1-3 413, MS2-1421, MS2-2 422, MS2-3 423, and MS2-4 424.

Data 601 602, such as network data, reaches the BSs 603 604 via somecommunication medium (not shown).

In addition, shared data such as shared control data 611 from the BS1603 is optionally reaching the BS2 604. The shared control data 611includes information or data about free resource blocks which wereassigned to the BS1 603, but are not planned to be used by the BS1.

The BSs 603 604 communicate with the MSs 411 412 413 421 422 423 424through radio channels, as described above with reference to FIG. 4.

In addition, concurrently, based on an embodiment of the presentinvention, additional data is being sent by the BS2 604 to some MSs,such as, by way of a non-limiting example, MS2-2 422, by using aresource block, currently unused by the BS1.

The BS2 604 is using the resource block in order to send additional datato the MS2-2 422.

It is noted that the BS2 604 is using one or more resource blocks, whichthe BS2 604 was not originally supposed to be using, but the BS2 604 isusing these resource blocks when they are known to be unused by the BS1,by virtue of communication between the BSs about the unused time slots.

In some embodiment of the invention the shared control data 611 includesinformation or data about free resource blocks which were assigned tothe BS1 603, but are not likely to be used by the BS1. These resourceblocks are not certainly free, but likely to be free.

The above comment about certainly free resource blocks and likely to befree resource blocks applies to further descriptions of resource reuseincluded herein with reference to FIGS. 5B, 6, 8, 9, 10, and 11.

Reference is now made to FIG. 5B, which is a simplified illustration oftwo BSs 603 604 constructed and operating according to an alternativeexample embodiment of the present invention, communicating with severalMSs.

The two base stations (BSs) 603 604 are depicted communicating withseveral exemplary mobile stations MS1-1 411, MS1-2 412, MS1-3 413, MS2-1421, MS2-2 422, MS2-3 423, and MS2-4 424.

Communication data, such as data 601 602, reaches the BSs 603 604 viasome communication medium (not shown).

In addition, shared data such as the shared control data 611 from theBS1 603 is optionally reaching the BS2 604. The shared control data 611includes information about free resource blocks which are assigned tothe BS1 603 and are not expected to be used.

Shared control data 612 from the BS2 604 is optionally reaching the BS1603. The shared control data 612 includes information about resourceblocks which were assigned to the BS2 604 but unused by the BS2 604.

The BSs 603 604 communicate with the MSs 411 412 413 421 422 423 424using the radio channel, as described above with reference to FIG. 4.

In addition, concurrently, based on an embodiment of the presentinvention, additional data is being sent to some MSs, such as, by way ofa non-limiting example, MS2-2 422, by using a resource block which wasassigned to the BS1 603 but unused or not expected to be used by the BS1603.

The BS2 604 is using the resource block in order to send additional datato the MS2-2 422.

It is noted that the BS2 604 is using one or more resource blocks whichthe BS1 603 was not, for example initially supposed to be using, whenthey are known to be unused by BS1 603, by virtue of communication aboutthe free resource blocks.

In an embodiment of the present invention, the shared control data 611612 is communicated between the base stations 603 604 in a peer-to-peerfashion. The base stations 603 604 communicate with each other and withother base stations, as depicted below with reference to FIGS. 8 and 10,with no central control.

In an alternative embodiment of the present invention, the sharedcontrol data 611 612 is communicated between the base stations 603 604under control of one or more controllers instructing the base stations603 604 how to allocate unused resource blocks, and/or the sharedcontrol data 611 612 may be communicated through the controller.

In some embodiments of the invention, the communication is optionallyperformed via a communication connection having a latency duration ofless than a time slot.

In another alternative embodiment of the present invention, the basestations 603 604 have a master-slave relationship. The master basestation optionally instructs the slave base station, via the sharedcontrol data 611 612, what unused resource blocks to use.

Having a peer-to-peer relationship enables each of the base stations 603604 to discover resource blocks unused by the peer and allocate them forits own use, as will be described in more detail below, with referenceto FIGS. 8-11.

Reference is now made to FIG. 6, which is a simplified illustration ofthe BSs and MSs of FIG. 5B, in an alternative application of the exampleembodiment of FIG. 5B.

The alternative application of the present invention uses unusedsub-channels and time slots of a two different base stations tocommunicate to mobile stations within communication distance of the twodifferent base stations.

The two base stations BS1 603 and BS2 604 are depicted communicatingwith several exemplary mobile stations MS1-1 411, MS1-2 412, MS1-3 413,MS2-1 421, MS2-2 422, MS2-3 423, and MS2-4 424. The communication isperformed using resource blocks, and may be one-way from a BS to an MS,one way from an MS to a BS, or two way communications between a BS andan MS.

Communication data 601 602 reaches the BS1 603 and the BS2 604 via somecommunication medium (not shown), such as, by way of a non-limitingexample, a wired network, a wireless network, or a combination of both.

In addition, shared control data 611 from the BS1 603 reaches the BS2604. The shared control data 611 includes data about free resourceblocks which are allocated to the BS1 603 and are not expected to beused.

Shared control data 613 from the BS2 604 reaches the BS1 603. The sharedcontrol data 613 includes data about free resource blocks which areallocated to the BS1 603 and are not expected to be used, and/or datawhich the BS2 604 needs to have the BS1 603 send to an MS.

The BSs 603 604 communicate with the MSs 411 412 413 421 422 423 424using radio communications, as described above with reference to FIG. 4.

In addition, concurrently, based on an embodiment of the presentinvention, the BS1 603 is optionally sending data to some MSs by usingfree, currently unused resource blocks. The data being sent may beadditional data, thereby adding to the volume of data being sent to someMSs, and/or the data may be redundant data, thereby enabling errorcorrection to be performed on the data.

At any specific time slot, the BS1 603 may be using a resource blockwhich would have been allocated to the BS2 604 according to prior art,in order to send additional data to the MS2-1 421 (see communication721) according to the embodiment of the present invention. The BS 1 603is also using resource blocks which would have been allocated to the BS2604 according to prior art, in order to send additional data: to theMS2-2 422 (see communication 722).

It is noted that the BS1 603 is using sub-channels which the BS1 605 wasnot supposed to be using, but the BS1 603 is using them in a time slotwhen the sub-channels are known to be free, by virtue of communicationabout the free time slots.

It is additionally noted that the BS1 603 is communicating to MSs whichare in a cell belonging to the BS2 604. The communication to anothercell may cause more errors, because of a larger distance, or because ofpossible interference. The higher error rate may not be suitable forsome uses, but may be suitable for other uses, such as, by way of anon-limiting example, data networks with error correction or with repeattransmission such as, by way of a non-limiting example, WiMAX andEthernet.

In an embodiment of the present invention, the shared control data 611613 is communicated between the base stations 603 604 in a peer-to-peerfashion. The base stations 603 604 communicate with each other and withother base stations, as depicted below with reference to FIGS. 8 and 10,with no central control.

In an alternative embodiment of the present invention, the sharedcontrol data 611 613 is communicated between the base stations 603 604under control of one or more controllers instructing the base stations603 604 how to allocate unused resource blocks, and/or the sharedcontrol data 611 613 may be communicated through the controller.

In another alternative embodiment of the present invention, the basestations 603 604 have a master-slave relationship. The master basestation, by way of a non-limiting example BS2 604, optionally instructsthe slave base station, BS1 603, via the shared control data 613, whatunused sub-channels and time slots to use. In yet another alternativeembodiment of the present invention, the master base station BS2 604optionally uses the shared control data 613 to communicate data via theslave base station BS1 603 and the additional lines of communication 721and 722.

Having a master slave relationship enables a first base station to use asecond base station for sending data which requires more bandwidth thanavailable to the first base station were the base stations not using theinvention.

There are several ways by which a BS can know what resource blocks arefree for use.

One way by which a BS can find out what resource blocks are free for useis by communicating with other BSs.

In some embodiments of the invention a BS optionally providesneighboring BSs with data about resource blocks the BS has beenallocated according to a reuse scheme, and is not planning to use,thereby letting the neighboring BSs know which resource blocks are free.The above is a push technology.

In some embodiments of the invention a BS optionally requestsneighboring BSs for data about resource blocks the neighboring BSs havebeen allocated or assigned according to a reuse scheme, and are notusing. The above is a pull technology.

In some embodiments of the invention a BS finds out what resource blocksare free for use by having a central coordination unit (not shown),which communicates with base stations, gather information about unusedresource blocks, and provide the information about unused resourceblocks to the base stations.

In some embodiments of the invention, the central coordination unit maybe included in one of the base stations, and/or several coordinationunits may be included in some of the base stations.

One way for the information to be provided to the base stations is bypush technology, that is, by letting each base station know whatresource blocks are free to be used by that base station. Another wayfor the information to be provided to the base stations is by pulltechnology, that is, by having a base station which requires additionalresource blocks request the central coordination unit for informationabout free resource blocks.

A central coordination unit may be overloaded, and/or may be distant,and/or may provide a single failure point for using free resourceblocks, so in some cases a distributed method may be preferred.

Communication between neighboring BSs, and/or between BSs and a centralcoordination unit, occurs in a time which shall be termed hereinlatency.

When the latency is substantially shorter than a time slot, BSsoptionally plan use of unused reuse resource blocks, and can startproviding communication based on the plan when the next time slotstarts. A “reuse resource block” is hereby defined as a unit of one timeslot in one sub-channel, selected from sub-channels which are allocatedfor use in a reuse scheme, such as, by way of a non-limiting example,the sub-channels allocated for use in a reuse ⅓ scheme. A typical timeslot lasts tens of microseconds in some cellular communication systems.

Latency of communication between neighboring BS, and/or between BSs anda central coordination unit, depends on how they communicate. Latencycan easily be 1 millisecond, when using broadband links between BSs.Good candidate for communication between the BSs are high speedmicrowave links, and fiber optic links.

When the latency is substantially equal to a time slot, using an unusedreuse resource block may still be done, especially when there are manyunused sub-channels. The disadvantage caused by interference may belower than the advantage provided by having additional resource blockscommunicate data. This is especially true of data networks with errorcorrection or with repeat transmission such as, by way of a non-limitingexample, Ethernet over WiMAX.

When the latency is substantially longer than a time slot, using anunused reuse resource block may still be done, but chances ofinterference due to unwanted simultaneous use of re-use sub-channels goup.

One way in which resource allocation in Time Division Duplexing (TDD) isimplemented, according to some embodiments of the present invention, isby dividing resource blocks into several groups of resource blocks. Eachgroup of resource blocks may include one or more resource blocks.

It is again noted that resource allocation in TDD is an example, andother resource allocation schemes suitable for optionally dividingresource blocks into several groups of resource blocks stand to improveresource use by using embodiments of the invention.

By way of a non-limiting example, three groups are described herein. Itis noted that two groups, and more than three groups are alsocontemplated, and the example of three groups is chosen for adescriptive purpose. Expansion to two groups or to more than threegroups is considered trivial for persons skilled in the art.

In an exemplary embodiment of the invention, UL and DL zones are dividedinto three groups of resource blocks. Each BS is assigned one group as aprimary resource, one group as a secondary resource, and one group as atertiary resource.

Reference is now made to FIG. 7, which is a simplified illustration of agrouping of resource blocks in a frame 800 constructed and operatingaccording to an example embodiment of the present invention.

The frame 800 includes the horizontal time axis 101 and the verticalfrequency axis 102 of FIG. 1. The frequency axis 102 depicts the severalreuse sub-channels 103 104 105 of FIG. 1. The time axis 101 depicts thetime frame, subdivided into a MAP zone 106, a DL zone 107, and a UL zone108 as in FIG. 1.

The sub-channels 103 104 105 are divided among BSs, for use incommunication with MSs. By way of a non-limiting example, two of thesub-channels are depicted which have been allocated to a first basestation BS1, and one of the sub-channels is depicted which has beenallocated to a second base station BS2.

The DL zone 107 of the first sub-channel 103 has been divided into aprimary group 801 for the BS1, a secondary group 802 for the BS1, and atertiary group 803 for the BS1. The UL zone 108 of the first sub-channel103 has been divided into a primary group 806 for the BS1, a secondarygroup 807 for the BS1, and a tertiary group 808 for the BS1.

The DL zone 107 of the second sub-channel 104 has been divided into aprimary group 811 for the BS1, a tertiary group 813 for the BS1, and asecondary group 812 for the BS1. The UL zone 108 of the secondsub-channel 103 has been divided into a primary group 816 for the BS1, atertiary group 818 for the BS1, and a secondary group 817 for the BS1.

The DL zone 107 of the third sub-channel 105 has been divided into aprimary group 821 for the BS2, a secondary group 822 for the BS2, and atertiary group 823 for the BS2. The UL zone 108 of the third sub-channel103 has been divided into a primary group 826 for the BS2, a secondarygroup 827 for the BS2, and a tertiary group 828 for the BS2.

Reference is now made to FIG. 8, which is a simplified illustration of anetwork of base stations constructed and operating according to anexample embodiment of the present invention, showing groups of reusesub-channels.

The network connects, by way of a non-limiting example, every basestation connected by the network to every one of six adjacentneighboring base stations, and to additional non-adjacent neighboringbase stations.

A first base station 901 is connected to 6 neighboring base stations 902903 904 905 906 907.

The first base station 901 has several resource blocks allocated as aprimary resource. The primary resource is depicted as a group 911. Thefirst base station 901 also has several resource blocks allocated as asecondary resource. The secondary resource is depicted as a group 912.The first base station 901 also has several resource blocks allocated asa tertiary resource. The tertiary resource is depicted as a group 913.

The neighboring base stations 902 903 904 905 906 907 have primaryresources depicted a groups 921 931 941 951 961 971, secondary resourcesdepicted as groups 922 932 942 952 962 972, and tertiary resourcesdepicted as groups 923 933 943 953 963 973.

Other base stations depicted in FIG. 8 are also depicted as havingprimary, secondary, and tertiary resources. The other base stations andresources are not marked by reference numbers, but their meaning isintended to be consistent with the explanation referring to the basestations and resources which are marked by reference numbers.

Three different patterns are used in FIG. 8, to depict three groups ofreuse resource blocks. The groups of reuse resource blocks are selectedso that no base stations have the same resource blocks serving as aprimary resource as their adjacent neighbors in the network. The groupsof resource blocks are also selected so that no base stations have thesame resource blocks serving as a secondary resource as their adjacentneighbors in the network, nor share the same resource blocks serving asa tertiary resource as their adjacent neighbors in the network.

Selection of three groups of resource blocks is a matter of selectingsub-channels and time slot combinations among the sub-channels and timeslot combinations available to the base stations.

Based on the above resource blocks mapping, optionally no base stationshould interfere with a neighboring base station when each is using itsprimary resources. When a need arises to use a resource block from asecondary resource, the base station optionally has data on which of itsneighbors has a resource block free for use. The data has optionallybeen transferred over the network.

An exemplary method for a base station to select which resource blocksto use for communication is now described.

Each base station optionally has data describing primary, secondary, andtertiary resource blocks of relevant neighbors. More relevant neighborsare adjacent neighbors, where interference may occur duringcommunication over the same resource block. Less relevant neighbors aremore distant neighbors, which would not cause interference whencommunicating over the same resource block, but could cause interferencewith adjacent neighbors is using the same resource block.

(a) Each base station transmits the number of resource blocks it plansto use to its adjacent neighbors.

(b) after receiving the data transmitted in (a), each BS selects whichresource blocks to use according to the following rules:

(b.1) each BS may freely use resource blocks from its primary resource;

(b.2) each BS may use that part of its secondary resource which has beenleft unused by adjacent neighbors which have the BS's secondary resourceas their primary resource;

(b.3) each BS may use that part of its tertiary resource which is notplanned to be used by adjacent neighbors which have the BS's tertiaryresource as their primary resource and/or secondary resource.

It is noted that every BS optionally allocates resources ordered byfrequency, so that other BSs may calculate which of their neighbor'sresources is free and/or is planned to be free. Other orderings are alsocontemplated, such as, without limiting generality: increasing order offrequency, decreasing order of frequency, and having a common table offrequency orders. A BS optionally knows a neighboring BS's order ofselecting resources.

It is noted that in order to use a tertiary resource, a BS needs to knowhow much of that resource is free. The BS's tertiary resource is also asecondary resource to some adjacent neighbors, therefore the BS does notimmediately know how much of its tertiary resource is free.

(c) after calculating which resource blocks a BS plans to use, the BStransmits its plan to its adjacent neighbors, which can then know whichtertiary resources will end up free to be used.

It is noted that the transmission may optionally be by multicasting,posting, and multi-unicasting.

Reference is now made to FIG. 9, which is a simplified flow chartillustration of a method for planning resource assignment, operatingaccording to an example embodiment of the present invention. The flowchart illustrates the method used by a BS to learn about unusedresources of neighboring BSs, and to provide information about its ownresource use to neighboring BSs.

Each base station schedules use of resources, defined above as resourceblocks, to be used in an exemplary time period X, at first optionallyusing its primary resources (1010).

Following the scheduling of primary resources, each base stationoptionally sends data about its unused primary resources to its adjacentneighbors (1020). If there are no unused primary resources the basestation may optionally send notice of no unused primary resources to itsadjacent neighbors.

Each base station then optionally receives the above communication,which provides data about unused resources from its adjacent neighbors(1030). The neighbors' unused resources may be additional resources forthe base station to use.

At this point, each base station may, for example, if it needs to useadditional resources, plan to use additional, for example secondary,resources which its adjacent neighbors have indicated they are not using(1040). The selection of additional resources is optionally madeaccording to an order as described in item (b.3) above.

At this time, having planned use of whatever primary and additional, forexample secondary, resources needed, the base station then executes theschedule for the time period X (1080), that is, communicates using theschedule.

The above described method includes two groups of resources: primaryresources and additional, or secondary, resources. Any number of groupsof resources may be chosen, and FIG. 9 additionally describes one moregroup of additional resources, for example tertiary resources. It isnoted that more groups of resources may be chosen.

When three groups of resources are included in the method, furtheractions include having:

The base station sends data about its unused resources to its adjacentneighbors (1050). If there are no unused resources the base station mayoptionally send notice of no unused resources to its adjacent neighbors.

Each base station receives the above communication, which provides dataabout unused resources from its adjacent neighbors (1060).

At this point, each base station may, if it needs to use additionalresources, plan to use yet additional, for example tertiary, resourceswhich its adjacent neighbors have indicated they are not using (1070).

Having planned use of whatever primary and additional, for examplesecondary and tertiary, resources needed, the base station then executesthe schedule for the time period X (1080), that is, communicates usingthe schedule.

It is noted that FIG. 9 describes the planning and execution of aschedule for a time period X. Embodiments of the invention do not limitto planning and execution for one time period X at a time. The abovedescription applies, mutatis mutandis, to planning of more than one timeperiod X at a time.

Reference is now made to FIG. 10, which is a simplified illustration ofcommunications and decisions on a timeline, with reference to basestations constructed and operational according to the example embodimentof FIG. 9.

FIG. 10 depicts the example of FIG. 9 with three groups of resources:primary resources, secondary resources, and tertiary resources. Threeparallel timelines 1101 1102 1103 are depicted. A first timeline 1101describes some of the events happening at a first base station (BS1),which corresponds to the base station 901 of FIG. 8. A second timeline1102 describes some of the events happening at base stations which areadjacent to the first base station, which correspond to the base station902 (BS2), the base station 904 (BS4), and the base station 906 (BS6) ofFIG. 8. A third timeline 1103 describes some of the events happening atother base stations, which are adjacent to the first base station, andwhich correspond to the base station 903 (BS3), the base station 905(BS5), and the base station 907 (BS7) of FIG. 8.

At a time of a first event 1110, BS1 sends data about its unused primaryresources to its adjacent neighbors, BSs 3, 5, 7 and BSs 2, 4, 6. TheBSs 3, 5, 7 also send data about their unused primary resources to,among others, BS1. The BSs 2, 4, 6 also send data about their unusedprimary resources to, among others, BS1. The data sent at the time ofthe first event 1110 is depicted by arrows 1120. The arrows have a fill(dots, diagonals, hatches) intended to correspond to the fills used inFIG. 8 for the resources of the BSs.

At a time of a second event 1111, the BSs, including BS1, receive thedata sent at the time of the first event 1110.

At a time of a third event 1112, BS1 allocates its secondary resources,and sends data about its unused secondary resources to its adjacentneighbors, BSs 3, 5, 7 and BSs 2, 4, 6. The BSs 3, 5, 7 also send dataabout their unused secondary resources to, among others, BS1. The BSs 2,4, 6 also send data about their unused secondary resources to, amongothers, BS1. The data sent at the time of the third event 1112 isdepicted by arrows 1122.

At a time of a fourth event 1113, the BSs, including BS1, receive thedata sent at the time of the third event 1112.

At a time of a fifth event 1114, BS1 allocates its tertiary resources.The BSs 3, 5, 7 and the BSs 2, 4, 6 also allocate their tertiaryresources.

Following the allocation of primary, secondary, and tertiary resources,the BSs optionally execute their frame allocations.

It is noted that the BSs may, if so desired and/or required, optionallyexecute frame allocations based on their primary allocations as soon asthe time of the first event 1110.

It is noted that the BSs may, if so desired and/or required, optionallyexecute frame allocations based on their secondary allocations as soonas the time of the third event 1112, and if they have not already doneso, the BSs may also optionally execute frame allocations based on theirprimary allocations as soon as the time of the third event 1112.

It is noted that the examples herein describe three portions ofresources which correspond to a hierarchy of three levels.

Reference is now made to FIG. 11, which is a simplified flow chartillustration of a method for planning resource assignment, operatingaccording to an alternative example embodiment of the present invention.

An additional method for a base station to select which resource blocksto use for communication is now described. The additional methodincludes the method described in FIG. 10, and additionally: thetransmission of (a) is sent to adjacent neighbors and also to adjacentneighbors of adjacent neighbors. Base stations can therefore calculate(b.1) (b.2) and (b.3) and use some parts of their tertiary resourcesalready after receiving the transmission of (a).

FIG. 10 depicts a method following the example of FIG. 9, with threegroups of resources: primary resources, secondary resources, andtertiary resources

Each base station schedules use of resources, defined above as resourceblocks, to be used in an exemplary frame X, at first using its primaryresources (1210).

Following the scheduling of primary resources, each base station sendsdata about its unused primary resources to its neighbors (1220). Thedata is sent at least to adjacent neighbors and to neighbors of adjacentneighbors. If there are no unused primary resources the base station mayoptionally send notice of no unused primary resources to its adjacentneighbors.

Each base station then receives the above communication, which providesdata about its secondary resources and its tertiary resources from itsneighbors (1230), both adjacent neighbors and at least adjacentneighbors of adjacent neighbors.

At this point, each base station may, if it needs to use additionalresources, plan to use secondary resources which its adjacent neighborshave indicated they are not using, and some tertiary resources which arecertain of not being used by neighbor base stations (1240).

Now the base station sends data about its unused secondary resources toits neighbors (1250). The data is sent at least to adjacent neighborsand to neighbors of adjacent neighbors. If there are no unused secondaryresources the base station may optionally send notice of no unusedsecondary resources to its neighbors.

Each base station then receives the above communication, which providesdata about its tertiary resources from its neighbors (1260), bothadjacent neighbors and at least adjacent neighbors of adjacentneighbors.

At this point, each base station may, if it needs to use additionalresources, plan to use tertiary resources which its neighbors haveindicated they are not using (1270).

Having planned use of whatever primary, secondary, and tertiaryresources needed, the base station then executes the exemplary frame X(1280), that is, communicating using frame X.

It is noted that each BS can then transmit its exact MAP allocation toits neighbors, plus a description of the data to be transmitted, as donein a Multicast Broadcast Services (MBS) portion of an OFDMA data frame.

It is noted that the neighbors may apply macro-diversity for specificMSs.

It is expected that during the life of a patent maturing from thisapplication many relevant reuse schemes, resource allocation schemes,OFDM communication schemes such as WiMAX and LTE, and Partially UsedSub-Carrier (PUSC) schemes will be developed and the scope of the termsreuse schemes, resource allocation schemes, and Partially UsedSub-Carrier (PUSC) schemes is intended to include all such newtechnologies a priori.

The terms “comprising”, “including”, “having” and their conjugates mean“including but not limited to”.

As used herein, the singular form “a”, “an” and “the” include pluralreferences unless the context clearly dictates otherwise. For example,the term “a unit” or “at least one unit” may include a plurality ofunits, including combinations thereof.

The word “exemplary” is used herein to mean “serving as an example,instance or illustration”. Any embodiment described as “exemplary” isnot necessarily to be construed as preferred or advantageous over otherembodiments and/or to exclude the incorporation of features from otherembodiments.

The word “optionally” is used herein to mean “is provided in someembodiments and not provided in other embodiments”. Any particularembodiment of the invention may include a plurality of “optional”features unless such features conflict.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention, which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable sub-combination or as suitable in any other describedembodiment of the invention. Certain features described in the contextof various embodiments are not to be considered essential features ofthose embodiments, unless the embodiment is inoperative without thoseelements.

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims.

All publications, patents and patent applications mentioned in thisspecification are herein incorporated in their entirety by referenceinto the specification, to the same extent as if each individualpublication, patent or patent application was specifically andindividually indicated to be incorporated herein by reference. Inaddition, citation or identification of any reference in thisapplication shall not be construed as an admission that such referenceis available as prior art to the present invention. To the extent thatsection headings are used, they should not be construed as necessarilylimiting.

1. A method of coordinating the use of communication resources in acellular network comprised of a plurality of base stations serving arespective cell, comprising: establishing a first, a second and a thirdfraction of communication resources available in the cellular network;for a first cell, a second cell and a third cell, adjacent to eachother, each served by a respective first, second and third base station,exchanging data between the first base station and mobile stationlocated at an edge of the first cell using the first fraction of thecommunication resources; exchanging data between the second base stationand mobile stations located at an edge of the second cell using thesecond fraction of the communication resources; exchanging data betweenthe third base station and mobile stations located at an edge of thethird cell using a third fraction of the communication resources.
 2. Amethod as claimed in claim 1, wherein each of the first, the second andthe third base station uses all three fractions as a primary resource,secondary resource and tertiary resource, based on the distance from therespective base station.
 3. A method as claimed in claim 2, wherein thefirst, the second and the third base station use a different fraction asa primary resource.
 4. A method as claimed in claim 2, wherein first,the second and the third base station use a different fraction as asecondary resource.
 5. A method as claimed in claim 2, wherein first,the second and the third base station use a different fraction as atertiary resource.
 6. A method as claimed in claim 1, wherein the first,second and third fractions are each ⅓ of the communication resourcesavailable in the cellular network.
 7. A method as claimed in claim 1,wherein the first, second and third fractions represent a differentpercentage of the communication resources available in the cellularnetwork.
 8. A method as claimed in claim 1, wherein the communicationresources are sub-channels of a frequency channel available in thecellular network for downlink communication.
 9. A method as claimed inclaim 1, wherein the communication resources are sub-channels of afrequency channel available in the cellular network for uplinkcommunication.
 10. A method as claimed in claim 1, wherein thecommunication resources are CDMA codes from a set of CDMA codesavailable in the cellular network for downlink communication.
 11. Amethod as claimed in claim 1, further comprising: transmitting from thefirst base station to the second base station information about aresource block in the first fraction which is not planned to be used bythe first base station; receiving the information at the second basestation and scheduling use of the first resource block for exchangingdata with mobile stations located at an edge of the second cell.
 12. Amethod as claimed in claim 1, further comprising: transmitting from thefirst base station to the second base station information about aresource block in the first fraction which is not planned to be used bythe first base station; transmitting from the second base station to thefirst base station data received at the second base station for a mobilestation located at an edge of the first cell; and receiving the data atthe first base station and scheduling use of the resource block forexchanging data with the mobile stations located at an edge of the firstcell.
 13. A method as claimed in claim 11, wherein the resource blockcomprises a communication resource which may cause interference, whenused simultaneously by the first and second base stations.
 14. A methodas claimed in claim 12, wherein the resource block comprises acommunication resource which may cause interference, when usedsimultaneously by any of the first, second and third base stations. 15.A method as claimed in claim 1 wherein the communication systemcomprises a Time Division Duplex (TDD) communication system.
 16. Amethod as claimed in claim 1 wherein the communication system comprisesa Frequency Division Duplex (FDD) communication system.
 17. A method asclaimed in claim 11, wherein the resource block is used by the thirdbase station.
 18. A method as claimed in claim 1, wherein the first,second and third base stations operate in a master-slave relationship,the first base station being the master.
 19. A method as claimed inclaim 1, wherein first, second and third base stations operate in apeer-to-peer relationship.